Who here used to watch All in the Family?
What did Archie Bunker say when he wanted someone else to be quiet?
I’m betting you just said “Stifle yourself!”
Now, some horsey people among the readers may wonder how a dislocated knee would cause someone to be quiet, but most of us are not familiar with that other word stifle, which as a noun refers to the joint on horses and similar animals that equates to the knee, and as a verb refers to dislocation of same. There’s no particular reason to think the two stifles have a common origin. But of course I wouldn’t want to stifle further etymological research. Especially since the origin of both words is entirely uncertain (French estouffer seems likely related to the non-horse [but not non-hoarse] one).
I also wouldn’t want to stifle innovation, dissent, competition, or creativity – or laughter. Maybe a yawn, though. All of these are things commonly spoken of as being subject to stifling. Or, more to the point, all these words are often seen after stifle – which itself may be preceded by trying to or could. The word stifling is actually a little different: the number one word to come after it, by a long chalk, at least in the Corpus of Contemporary American English, is heat.
And why would anyone want to stifle heat? They wouldn’t, of course. Nor would they want to be stifled by it, but it’s quite something how often people can speak of the heat as being stifling. Especially since you would think that if the heat is stifling them, they wouldn’t be able to speak. (And why are stifling creativity and stifling heat operating in opposite directions? One stifling is a present participle and the other is an adjective formed from the same.)
Well, figurative is figurative, eh? How often do people speak of stifling literally? As in causing the death of someone or something by depriving of oxygen? They may sometimes use smother or suffocate that way, but whereas He smothered the dog or He suffocated the dog might be taken to mean the dog had been killed, He stifled the dog would much more likely be taken to mean the dog had simply been silenced one way or another (but probably not by death).
And why do we need three words for basically the same thing? Well, in part because they have little differences of connotation and usage patterns – smother, for instance, generally produces an image of something soft being held over the face (and has the added flavour of its culinary use: steak smothered in mushrooms is acceptable; steak stifled in mushrooms or steak suffocated in mushrooms is not); suffocate seems to focus more on the sensation of asphyxiation; stifle, as we have seen, carries more of a sense of silencing or impairing.
But they also have different tastes from the feel and sound of them. True, they all start with /s/; two of them also have /f/. (And we think again of asphyxiation, which is the most literal of the bunch but does not automatically refer to an act of one person on another.) But suffocate has more of a gasping or coughing sound, and an echo of suffering; on the other hand, smother has a well-known rhyme in mother, and some other echoes too. Stifle has the cutting edge of the /aI/ central dipthong, which sounds like an exclamation of pain or woe and gives it a taste in the vein of rifle and knife, not to mention life, which may be ending. But probably not literally. (It also echoes Eiffel, as in Tower, but the different spelling attentuates that influence; those who hear it are more likely to think of a Bunker.)